An Investigation of the Influence of Deep-Bar Effect on the Resistance of Cage Rotor End-Rings

A method by which the influence that skin effect in the bars of a cage rotor has on the resistance of the end-rings can be determined numerically is outlined. The method is based on the use of a finite-element model of a portion of the end-ring comprising one rotor slot-pitch and centered on a rotor bar. Numerical results are presented for two particular cage geometries using the data of two commercially manufactured machines. The results indicate that, in machines in which deep-bar effect is important, the consequential changes in rotor end-ring resistance for the fundamental field may be significant. For the harmonics, however, the relatively low magnitude of the end-ring resistance renders deep-bar corrections unnecessary.